This invention relates to roller tappets or cam followers of the type used in some internal combustion engines and, more particularly, to an improved roller follower having positive means for lubricating the roller.
Roller followers are typically used in diesel engines or in high performance engines in place of conventional tappets to provide improved engine breathing by allowing increased valve lift velocity without increasing the tappet body diameter. In U.S. Pat. No. 4,361,120, a hydraulic roller follower is described wherein a recess is provided at the lower end of the follower which substantially encloses a roller rotatably mounted therein on a pin except for a small amount of the lower roller periphery to permit contact with the engine cam. Although this design is said to be an improvement over previous roller followers by providing additional strength in the lower end, it accentuates the problems caused by poor lubrication between the roller and the pin forming its rotational axis. Lubrication of roller cam followers, including the foregoing described follower has previously depended on splash or leaking of oil through the tappet bore of the crankcase. Poor lubrication between the cam follower roller and its mounting pin leads to reduced life of the bearing surfaces and eventual seizure of the roller on the pin and failure of the camshaft lobe due to increased wear.